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Understanding Uncertainties in Paleoclimate and Paleoecology: Age Models, Proxy Processes, and Beyond | December 18, 2014
GUARDING AGAINST FALSE DISCOVERY
IN LARGE-SCALE DENDRO
CHRONOLOGYSco! St. George
University of Minnesota
3ASSERTIONS BASED ON
TREE-RING DATA
COSMICRAYS
“ ”Dengel et al., 2009
New Phytologist
… THERE WAS A CONSISTANT AND SIGNIFICANT RELATIONSHIP
BETWEEN GROWTH OF THE TREES
AND THE FLUX DENSITY OF GALACTIC COSMIC RADIATION.
SOLARCYCLE
“ ”
Duan and Zhang, 2014 Journal of Geophysical Research - Atmospheres
SPECTRAL ANALYSIS ALSO SHOW THAT SIGNIFICANT PERIODICITIES
OF ~11 YEAR, 54 YEAR, AND 204 YEAR PEAKS [IN TREE-RING DENSITY RECORDS]
RESPOND TO THE SCHWABE CYCLE,
THE FOURTH HARMONIC OF THE SUESS CYCLE, AND THE SUESS CYCLE,
RESPECTIVELY.
ATLANTIC MULTIDECADAL
OSCILLATION
“ ”Maxwell et al., 2013
Agricultural and Forest Meteorology
TUPELO HONEY YIELD-PER-HIVE [RECONSTRUCTED FROM TREE-RING WIDTHS]
HAS OSCILLATED BETWEEN MULTIDECADAL-LENGTH PERIODS OF LOW AND HIGH YIELDS
DURING THE PAST 211 YEARS AND IS ASSOCIATED WITH
THE ATLANTIC MULTIDECADAL OSCILLATION.
LARGE-SCALE GEOPHYSICAL PHENOMENA
SMALL SETS OF TREE-RING WIDTH
DATA
BOTTOM-UP APPROACH
JUNE TEMPERATURE JULY TEMPERATURE
AUGUST TEMPERATURE SEPTEMBER TEMPERATURE
OCTOBER TEMPERATURE NOVEMBER TEMPERATURE DECEMBER TEMPERATURE
JANUARY TEMPERATURE FEBRUARY TEMPERATURE
MARCH TEMPERATURE APRIL TEMPERATURE
MAY TEMPERATURE JUNE TEMPERATURE JULY TEMPERATURE
AUGUST TEMPERATURE SEPTEMBER TEMPERATURE
p > 0.05
TYPE 1 ERROR
PinusPicea
QuercusPseudotsuga
Larix
NothofagusAustrocedrisPhyllocladus
Agathis
Source: St. George, PAGES News, 2014
There are more than 3,200 publicly-available tree-ring records (and many more held by individual investigators).
FALSE DISCOVERY
RATE
“ ”Wilks, 2006
Journal of Applied Meteorology and Climatology
… THE EXPECTED PROPORTION OF REJECTED LOCAL NULL HYPOTHESIS
THAT ARE ACTUALLY TRUE.
SYNOPTIC APPROACH
PiceaPinus
PseudotsugaQuercusLarix
A
C
# re
cord
s
% re
cord
sB
18ºN
36ºN
54ºN
72ºN90ºN
120ºW 60ºW 0º 60ºE 120ºE 180ºW180ºW
1000 20001200 1400 1600 1800
2000
1000
0 0%
12%
6%
1000 20001200 1400 1600 1800Year Year
0º
Source: St. George et al., Geophysical Research Le!ers, 2013
This map illustrates the reasonably-large subset of the North American tree-ring width network
analyzed by this study.
STRONG WIDESPREAD
DIRECT
-0.8 -0.6 -0.4 -0.2 +0.2 +0.4 +0.6 +0.8
correlation coefficient (ring-width vs. climate)
(a) Winter precipitation
(b) Summer precipitation
(c) Summer temperature
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6
WINTER PRECIPITATION
Source: St. George, Quaternary Science Reviews, 2014
Fri!s, H.C. Growth-rings of trees: their correlation with climate. Science 154, 973-975 (1966).
EL NIÑOSOUTHERN OSCILLATION
(a) El Niño-Southern Oscillation
(b) Pacific Decadal Oscillation
(c) Atlantic Multidecadal Oscillation
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6
ENSO
Source: St. George, Quaternary Science Reviews, 2014
WEAK(ER) UNCOMMON
INDIRECT
ATLANTIC MULTIDECADAL
OSCILLATION
(a) El Niño-Southern Oscillation
(b) Pacific Decadal Oscillation
(c) Atlantic Multidecadal Oscillation
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6
Source: St. George, Quaternary Science Reviews, 2014
ATLANTIC MULTIDECADAL OSCILLATION
PACIFIC/ NORTH AMERICAN
PATTERN
(d) Pacific/North-American Pattern
(e) North Atlantic Oscillation
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6
PACIFIC/NORTH AMERICAN PATTERN
Source: St. George, Quaternary Science Reviews, 2014
ENSO PNA475/2270 records
139/2270 records
p > 0.05
TYPE 1 ERROR
3POTENTIALLY-USEFUL APPROACHES TO ADDRESS
THIS CHALLENGE
1STATISTICAL SIMULATIONS
Dr. Dave Meko University of Arizona
EXACT SIMULATION
0
+200
1900 1920 1940 1960 1980 2000
precipitation anomaly (mm)
-200
decadal target
decadal ‘noise’
Source: St. George and Ault, Journal of Geophysical Research - Atmospheres, 2011
2FORWARD MODELLING
Dr. Eugene Vaganov Siberian Federal University
Source: Vaganov et al., In Dendroclimatology, 2010
180oW 120oW 60oW 0o 60oE 120oE 180oW
15oN
30oN
45oN
60oN
75oN
90oN
180oW 120oW 60oW 0o 60oE 120oE 180oW
15oN
30oN
45oN
60oN
75oN
90oN 1.00.80.60.40.20.0
Synthetic tree-ring records generated by a forward model (and modern climate data) exhibit largely the same spatial pa!erns in climate response as real trees.
Can we predict how local trees should respond to weak or remote climate influences?
SOIL MOISTURE : TEMPERATURE
Source: Xiaolu (Grace) Li, Cornell University
3SELECTIONCRITERIA
PinusPicea
QuercusPseudotsuga
Larix
NothofagusAustrocedrisPhyllocladus
Agathis
Source: St. George, PAGES News, 2014
Because the global ring-width network is now so large, it is crucial to ensure our understanding of tree-environment relations is not influenced
by decisions to include or exclude particular records.